1. Field of the Invention
The present invention relates to a method to encrypt information that is transferred between two communication units. The communication units may be mobile telephones, personal computers, electronic tablets, palm-top computers, etc. The present invention will be described below, however, for the case in which the communication units are mobile telephones. Therefore, the term “mobile telephone” is used below and in the claims to denote a communication unit of the type specified above. The term “information” is used to denote a voice conversation and the transfer of data between two communication units. The transfer of data comprises the transfer of images. With respect to the transfer of information between two mobile telephones, this is also referred to using the term “telephone call”.
2. Description of the Related Art
There is a need to encrypt information that is transferred between two mobile telephones such that it is not possible for a third party to eavesdrop on conversations and data.
One way of achieving the encryption of telephone calls is to realise a security application on an SD card, which is inserted into a card-holder location in the mobile telephone. The information is in this way passed across an interface between the CPU of the mobile telephone, with its associated memory, and the said SD card. One problem with sending streams of data between an application on an SD card and the mobile telephone is that the limiting resources of the mobile telephone are used, in that the said interface has a limited capacity for the transfer of data. In many cases, the transfer requires so much resources that the function cannot be carried out. A second problem is that such a transfer of data leads to the consumption of power becoming so high that the battery duration is severely reduced. A third problem is that an encryption key, which is present in the memory of the mobile telephone, is exposed in an insecure environment.